In cellular networks, carriers provide services to mobile devices (e.g., cellular phones) that are registered as subscribers. The cellular network of the carrier that the mobile device subscribes to may also be referred to as the “home mobile network” or “home network” of the device. Staying within the coverage area provided by the home network is typically desirable for mobile users because the home network provides many services that roaming networks (and areas with no coverage) are unable to adequately provide. For example, voice services in a roaming network may be undesirable because of expensive roaming fees. Furthermore, some services may be unavailable to a mobile user while roaming. For example, the home network may provide text or multimedia messaging services (SMS or MMS) that are unavailable at the roaming network. In some circumstances, prospective roaming networks may use technologies that are incompatible with the mobile device itself (e.g., CDMA vs. W-CDMA), and therefore no services at all may be available to the mobile user while outside of the coverage area of the home network.
While home networks provide the widest range of services to the user, a user may often take their mobile device beyond the range of the home network. For example, the home network may be unavailable during an international business trip. During this time, mobile users desire the services provided by the home network, but are unable to register with the home network in order to receive those services.
Existing technologies provide partial solutions to the problem at hand, but each of these technologies has drawbacks. For example, the mobile device may support applications (apps) that allow the user to access the internet and make a Voice over Internet Protocol (VoIP) call. However, VoIP does not allow the user to use all of the features of their device that would normally be available in the home network (e.g., text, picture, and video messaging, location-based services, message-waiting indicators, and various other applications on the device that expect a standard backhaul interface to the carrier).
Another existing solution includes using the mobile device to contact a separate device that signals over licensed bands that the mobile device can interpret (i.e., using existing cellular protocols) and is connected to the internet. Unfortunately, during roaming travel, it may be illegal to signal over a licensed band with one of these separate devices (i.e., because the band is already licensed to another party). Additionally, the range for these separate devices that signal over licensed bands may be undesirably small (e.g., 5 mm or less) in order to minimize their interference with cellular networks that legally use the licensed spectrum.
Thus, it remains a problem to provide services of the home network to mobile devices while they are beyond the home network's coverage area.